This invention relates to binocular lens systems which comprise ophthalmic lenses. The lenses may be adapted for implantation in an eye such as intraocular lenses(IOLS) or adapted to be disposed on or in the cornea such as contact lenses or corneal inlays.
When functioning normally, the natural lens of the eye is somewhat elastic and therefore enables good vision of objects at all distances. However, when the natural lens is removed as a result of disease or injury and replaced with an IOL, the natural ability of the eye to accommodate is lost completely. However, an ability to have adequate vision at different distances without using spectacles can be provided by the IOL which is implanted following removal of the natural lens. To this end, the IOL may be multifocal as shown and described, for example, in Portney U.S. Pat. No. 5,225,858, Roffman et al U.S. Pat. No. 5,448,312 or Menezes et al U.S. Pat. No. 5,682,223. Alterhatively, the IOL may be of the type which is accommodating in that it can be moved by the eye itself as shown and described in commonly assigned application Ser. No. 09/532,910 filed Mar. 22, 2000 or monofocal with a depth of focus feature as shown and described in Portney. U.S. Pat. No. 5,864,378.
Another approach to overcoming loss of accommodation is to use ophthalmic lenses, such as contact lenses or IOLS, with different optical characteristics for each eye. For example with a system known as monovision one lens has a distance vision correction power and the other lens has a near vision correction power. Another example is shown and described in Roffman et al U.S. Pat. No. 5,485,228. It is also known to implant a distant dominant multifocal IOL in one eye and a near dominant multifocal IOL in the other eye as disclosed in the January 1999 issue of Clinical Sciences by Jacobi et al entitled xe2x80x9cBilateral Implantation of Asymmetrical Diffractive Multifocal Intraocular Lenses,xe2x80x9d pages 17-23.
Ophthalmic multifocal lenses can also be provided with some depth of focus. This is shown and described, for example, in Portney U.S. Pat. No. 5,225,858 and Roffman et al U.S. Pat. No. 5,684,560.
Whether monovision or multifocal ophthalmic lenses are employed, nighttime images may not be the same for both eyes and/or possess halos as when the headlights of an oncoming vehicle are observed. This can significantly reduce the ability of the observer to identify and locate objects near the headlights. For example, halos tend to be created when the patient views a distant object through the near vision portion of a multifocal lens, and the greater the add power, the more perceptible is the halo.
For example, this is shown and described in commonly assigned application Ser. No. 09/302,977 filed on Apr. 30, 1999. This application discloses a reduced add power multifocal IOL which reduces the effects of halos. This reduced add power IOL is implanted in a phakic eye in which the natural lens has lost some degree of accommodation, i.e. in partially presbyopic eyes.
The disclosure of each of the patent applications and patents identified herein is incorporated in its entirety herein by reference.
New binocular ophthalmic lens systems have been discovered. The present lens systems provide a combined effect of enhancing distance, intermediate and near visual function. In particular, the lens system are very effective in enhancing intermediate vision. Other important advantages are obtained. In general, the present lens systems comprise two lenses. The ophthalmic lens systems of this invention may include first and second lenses for use with first and second eyes of a patient, respectively. Each of the first and second lenses has more than one vision correction power and is therefore multifocal. Although this invention is particularly adapted for IOLS, it is also applicable to lenses which can be disposed on or in the cornea such as contact lenses and corneal inlays.
One lens, the first lens, provides the best image quality for distance or distant objects. The other lens, the second lens, provides the best image quality for near objects. As such, the present lens systems operate.in part like a monofocal monovision pair. Each lens preferably contains a larger depth of focus than conventional monofocal lens designs. The depth of focus of the first lens preferably ranges from distance to intermediate distances. The depth of focus of the second lens preferably ranges from near to intermediate distances. The extended depth of focus is believed to reduce the disparity in functional vision eyes and to at least reduce the size and/or the occurrence of multifocal lens halos.
The first lens is biased for distance vision or distance biased. This may be accomplished, for example, by configuring the first lens so that the best visual acuity provided by the lens is for distant objects, for example, objects at infinity. The first lens provides better visual acuity for objects at infinity than the second lens. Preferably, the first lens substantially optimizes visual acuity from distance to intermediate distances. The first lens has a power including a maximum add power which is less than the add power for full near vision correction for the patient. Advantageously, the maximum add power of the first lens is no greater than about an add power for intermediate vision. The power of the first lens preferably varies from about the power for distance vision to the add power for intermediate vision. For example, the maximum add power of the first lens may be no more than about 1.5 diopters or about 1.75 diopters. All of the add powers set forth herein are in the spectacle plane. The first lens preferably has a power including a power required for distance vision correction for the patient.
The second lens is near biased. This may be accomplished, for example, by configuring the second lens so that the best visual acuity provided by the second lens is for objects at near distances. Alternatively, or in addition thereto, the second lens provides better visual acuity from intermediate to near distances, and in particular at near distances, than the first lens. Preferably, the second lens enhances visual acuity from intermediate to near distances. The second lens advantageously has a power including an add power for near vision. The minimum add power of the second lens preferably is no greater than about an add power for intermediate vision. In addition to the advantages noted above, the enhanced visual acuity of the second lens significantly enhances near vision and image quality.
The lenses can be made to have the relatively larger ranges of vision in various ways. For example, this can be accomplished by appropriately splitting the light between distance, intermediate and-near. Thus, the second lens may focus sufficient light to a near focus region so as to contribute to the second lens providing enhanced vision and better visual acuity from intermediate to near distance.
Alternatively or in addition thereto, the depth of focus of the zone or zones of the lens which provide intermediate vision correction may be appropriately increased to provide the second lens with enhanced vision characteristics from intermediate to near distances. This may be accomplished, for example, by controlling the aspheric surface design of the lenses. More specifically, the first and second lenses may each have a zone with an add power for intermediate vision correction with such zone having optical aberrations which increase the depth of focus of such zone. In one preferred embodiment, such zones extend radially outwardly and have progressively changing add powers as the zones extend radially outwardly.
The add power of the first lens is reduced over what it would be if the lens had the full or even nearly full add power, required for near vision correction. The reduced add power significantly reduces multifocal lens halos, such as those halos which occur in any eye because of the relatively large add power component, e.g., full or nearly full near vision add power, found in many multifocal lens designs.
In the interest of keeping the add power low while providing adequate vision quality, preferably the maximum add power of the first lens is no greater than about the power required for intermediate vision correction. By way of example, the maximum add power for the first lens may be from about 0.5 diopter to about 1.75 diopters and is preferably from about 1 diopter to about 1.5 diopters. The full or complete near vision correction can range from greater than about 1.75 diopters of add power, and is typically between about 2.0 diopters or about 2.5 diopters and about 3.0 or more diopters of add power.
The first and second lenses are adapted to provide some depth of focus. The first and second lenses preferably provide some depth of focus toward intermediate vision correction.
Each of the first and second lenses has an optical axis. Preferably the power of the first lens is different at a plurality of locations radially outwardly of the optical axis of the first lens, and the power of the second lens is different at a plurality of locations radially outwardly of the optical axis of the second lens.
Viewed from a different perspective, the power of each of the first and second lenses changes along a power curve, for example, in a radially outward direction from the associated optical axis. The power curve for the first lens is different from the power curve for the second lens. The power curve of the first lens may at least contribute to the first lens having good visual acuity from distance to intermediate distances and the power curve of the second lens may at least contribute to the second lens having good visual acuity from intermediate to near distances. The first lens may have a power which varies from about the power required for far vision correction to about a power required for intermediate vision correction. The second lens may have a power which varies from a power required for intermediate vision correction to the power required for near vision correction.
In one preferred embodiment, the first lens has first, second and third optical zones arranged radially with respect to the optical axis of the first lens with the second zone being intermediate or between the first and third zones and having a greater add power than either of the first and third zones. The second lens has first, second and third optical zones arranged radially with respect to the optical axis of the second lens with the second zone being intermediate or between the first and third zones and having a reduced add power than either of the first and third zones of the second lens.
Although the zones can be of various configurations, they are preferably substantially annular and substantially concentric. Preferably, there are at least two zones. Still more preferably, there are three or five of the zones with the innermost and outermost of the zones of the first lens having a power for far vision correction and the innermost and outermost of the zones of the second lens having a power for intermediate vision correction.
The power in a radial direction can change either gradually or abruptly. In one form of the invention, each of the second zones has a power which is substantially constant, and the area, for example, the annular area, of the second zone of the second lens is larger than the area of the second zone of the first lens. This also contributes to the second lens having better visual acuity from intermediate to near than the first lens.
IOLS constructed in accordance with this invention preferably are implanted following removal of the natural lenses, although they may be adapted for implantation in phakic eyes having some residual accommodation.
According to one aspect of the method of this invention, first and second ophthalmic lenses having different optical characteristics are placed on or in the eyes, respectively, of the patient. The first lens has better visual acuity for objects at infinity than the second lens. The second lens has better visual acuity for near distances than the first lens. The maximum add power of the first lens is less than the add power required for near vision correction. Preferably the ophthalmic lenses are IOLs and the step of placing includes implanting the first and second lenses in the eye, respectively, of the patient, for example, after removal of the patient""s natural lenses.
According to another feature of the method of this invention, first and second IOLs having different optical characteristics are placed on or implanted in the eyes, respectively, of a patient. The first lens having a power which varies between about a far vision power and about an intermediate power, and having a maximum power which is less than the add power required for near vision for the patient. The second lens provides better visual acuity for objects at near distances than the first lens.
Although the first and second lenses of the present inventions may be contacts or corneal inlays, the features of this invention are particularly adapted for IOLS which can be implanted, respectively, in the eyes of the patient, preferably a patient whose natural lenses have been removed.
Any and all features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.
The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.